Underwater communication transducers



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Filed Oct.

Feb EL 19% G. J. SEBESTA 3,4275% UNDERWATER COMMUNICATION TRANSDUCERS Filed Oct. 6, 1966 INVENTOR, GEORGE d SEBESTA Feb H, W69

G. J. SEBESFA UNDERWATER COMMUNJLCATION TRANSDUCERS 3 off Sheet Filed Oct. 6, 1966 INVENTOR, GEORGE J. SEESTA ATTORN EY United States Patent 3,427,579 UNDERWATER CGMMUNTCATTGN TRANSDUEELES George J. Sebesta, Huntington Hay, N (2% Frank Road, Tilicksvilie, NH. ltlzitill) Filed @ct. 6, 1966, der. No. 584,696 US. Cl. 34t3-l4 int. Cl. HtMh 13/02 17 (Iiaims This invention relates to voice communication transducers for underwater use, and more particularly relates to novel small microphonereceiver units worn on ones head for unhindered conversing with others while submerged under water.

The transducer headset of the present invention is effectively operable from near-surface to several hundred feet below. It is a compact rugged unit, with two parallel diaphragms each having an inertial type of transducer mounted thereon. They are contained within a common housing. The two transducers serve as microphone and reproducer, and are hermetically sealed against Water intrusion. The microphone side of the headset is positioned in contact with the head, and thereby picks up speech of the swimmer or diver. The reproducer unit mounted thereover generates and radiates received signals through the water a sound waves over a distance of several feet. The submerged person thus readily hears the produced sounds directly through the water, with his ears exposed and comfortably free-flooded While under pressure conditions. Others nearby him can also hear these radiated sound waves.

Previous underwater headsets had the problem of mounting their microphone and reproducers so as to permit mobility and retain visibility, as through a scuba face mask. In one such apparatus a microphone is mounted on the lower half of the face mask, at a pressurerelief compartment projecting forward. Such arrangement obstructs the vision of the wearer. Receivers are often worn on a separate headband over the ears Within the helmet. These are capable of providing good reception, but jeopardize airtightness of the helmet seal to the head, and also interferes with free flooding of the ears. In general, carbon microphones have heretofore been used. Such microphones have a number of limitations that the invention system overcomes, namely: direct current requirement, lack of linearity and smoothness of frequency response, and unstable operation under the widely varying static pressure typical of underwater operation.

The microphone hereof is a variable-reluctance, inertial type transducer, brought up to the output level of a carbon microphone with suitable amplification. Inertial-type microphones are intrinsically well suited to underwater application. A cranial position of this microphone works out very favorably. The microphone and reproducer headset of this invention is readily applied to the top of the head in combination with a scuba breathing mask. Consonants are transmitted to the head in better proportion to vowels than by the throat type. Also, such headset and helmet can advantageously be worn without the full face mask, with a breathing tube held in the mouth and the diver articulating carefully. The composite transducer unit hereof weighs a fraction of a pound; is less than two inches in diameter, and is about one-half inch thick. Its frequency range provides excellent intelligibility, with low background noise.

The invention systems provides direct hearing through both ears, and through the skull, as it too is coupled to the water sound vibrations. As the divers ears are unencumbered he is free to hear normal sea sounds, adding to his safety under water. Any type of breathing apparatus may be used with the invention transducer system, without modification. The transducers are small, electromechanical and reliable. They may be safey stored over long periods. They are completely sealed and waterproofed and thus undamaged by water, oxygen or atmospheric conditions. Their operation remains unaffected by the increased static pressure of greater depths. The communication system hereof is light in weight and compact; it is convenient, and comfortable for the diver; it provides good quality of communication, even in deep submergence; it does not interfere with the use or usefulness of conventional diving equipment, permitting full mobility and visibility.

The above and other features, objects and advantages of the present invention are set forth in the following description of an exemplary embodiment thereof, illustrated in the accompanying drawings, in which:

FIG. 1 shows the head of a diver wearing a scuba breathing mask and the exemplary headset.

FIG. 2 is a plan view of the dual transducer headset.

FIG. 3 is an elevational view of the headset unit of FIG. 2.

FIG. 4 is a central cross-sectional view through the unit of FIGS. 2 and 3, with the reproducer section shown separated.

FIG. 5 is an exploded perspective view of the exemplary headset unit, showing its basic components.

FIG. 6 is a cross-sectional view through a modified unit in accordance with this invention.

FIG. 7 is an enlarged elevational view of the interior of the single-transducer unit of FIG. 6, as seen from the right side thereof, partially in cross-section.

FIG. 8 is an enlarged showing of the transducer per se of FIG. 7, in perspective view.

In the preferred use of the invention communication system the headset 10 i mounted upon the head somewhat above the forehead, as shown in FIG. 1. Rubber straps 1T, 12 have ends fastened to unit 10, extend about the head and face, and serve as a chin strap 15. Bands 16, 17 hold the breathing scuba type mask 18 in position onto the face. A top strap 19 overlies unit 10 and holds it firmly onto the head, and also retains the upper portion of the face mask. The scuba mask 18 is conventional. No portion of the communication system hereof is located therein. The scuba breathing, visibility and mobility of the diver or swimmer are unimpeded.

The small light-weight transducer unit 10 is out of the way in use. It is firmly pressed against the head by its straps 11, 12 in conjunction with the mask support. An electrical cable 20 connects unit 10 to an amplifier (not shown). Its microphone output is thereby amplified and conducted or transmitted to a remote station or swimmer. The signal input for the reproducer section is conducted thereto through cable 20. Suitable interconnections, amplification and electrical filtering are provided in a well-known manner, and form no part of the present invention. The incoming signals are converted to omnidirectional sound output in the water. The portion of transducer headset 10 that contacts the head is the diaphragm of the microphone section, as will be set forth.

Thus conversation of the user is converted into corresponding audio signals that are thereupon amplified and conducted to a remote reproducer, for the communication. A push-to-talk switch is commonly used, and is optional herein.

FIG. 2 is a plan view of composite transducer unit 10, as seen from above at the reproducer sound output side; FIG. 3, an elevational view, with the cable set behind; and FIG. 4, a generally central cross-section therethrough, separated for illustrative purposes. Strap mounts 21, 22 are secured to the sides of the transducer housing 23. The microphone transducer 24- and reproducer 25 are mounted side by side within a cavity 26 in housing 23; unit 24 being fastened to the diaphragm-base 27 of the housing by machine screws 28; unit 25 to the upper diaphragm 29, by machine screws 30. A metal disc 31 is secured as by soldering to diaphragm 29 as a stiffener, mass load, and sound plunger as hereinafter set forth. Cable 20 couples through an opening 32 in the housing, with threaded bushing 33 and cable lock-nut 34. The cable contains conductors that electrically connect with the coil leads of the electromechanical transducers 24, 25, and the system circuit.

The housing 23 is preferably made of non-corrosive tough metal, as bronze or aluminum alloy, for mechanical stability and ruggedness of assembly. Further, the mass of housing 23 importantly enters into the dynamic characteristic of the transducer design and operation, as will be set forth hereinafter. The base 27 of housing 23 is of substantial thickness and strength to support the microphone inertial unit 24; withstand deep sea pressures; and press upon the head for coupling with skull vibrations due to speech.

A suitable thickness for the diaphragm 27 has been found to be of the order of 0.060. A boss 35 contains two apertures through which machine screws 28 fasten microphone unit 24 firmly with the diaphragm 27. An annular gap 36 extends between the frame 37 of unit 24 and boss 35, as screws 28 secure it with the armature 40 therewithin (see FIG. 5). Also, frame 37 is held above diaphragm 27 through gap 38. In this manner, the inertial reaction variable reluctance microphone 24 is supported for its vibratory action with respect to diaphragm 27 and the remainder of headset 10.

The reproducer inertial unit 25 is securely mounted with the diaphragm-disc assembly 29, 31 through machine screws 30. In the exemplary headset 10, the effective outer diameter of the vibratory annular portion of the thin diaphragm 29 that extends to the clamping ring 40 is 1.5"; and stiffened by disc 31 to an inner diameter of 1.0". The pliant annular diaphragm section hereof is thus A" wide, with a mass-loaded central section at piston-disc 31. The effective vibratory composite diaphragm 29, 31 has the mass effect of disc 31 to desirably lower the mechanical resonance frequency of the reproducer portion of the headset, to below that of the microphone portion.

The disc 31 is an effective plane piston of substantial forward area for coupling with the water when submerged to generate and radiate sound vibrations therein. Such combination has been found very effective to provide strong, clear sound wave propagation from near surface to several hundred feet in depth. The sound is heard by other divers, with their ears free flooded in the water, to at least a three foot radial distance from piston 31. The wearer of headset 10 thus readily hears the re produced sound therefrom.

The plane piston 31 is vibrated by the inertial action of reproducer 25, and in action is effectively isolated from the housing 23 by the deformable annular section of diaphragm 29. This combination importantly also serves as a mechanical filter to substantially separate the individual frequency characteristic actions of the microphone 24 and reproducer 25. Nevertheless, it has been found that said annular deformable diaphragm section advantageously couples the microphone-diaphragm 24, 27 and reproducer-piston 25, 31 across their common frame or housing 23 in their resultant subjective overall frequency response in operation underwater. The added stiffness to diaphragm 29 provided by disc 31 prevents its cave-in in deep depths due to static water pressure.

The composite headset 10 is compact. The microphone element 24 is offset with respect to reproducer element 25, as shown in FIG. 2. The exemplary elements 24 and 25 are each about /a long, /2 wide, and A" thick. They readily fit into rectangular cavity 26 in cylindrical housing 23, in side-oy-side relation. They are respectively firmly mounted with the two spaced and parallel diaphragms 27, 29. The whole is basically small, light in weight, yet very effective electromechanically and ample acoustically. Amplification is readily provided by an inconspicuous transistor amplifier. Amplification of the order of 45 db is adequate. The exemplary reproducer signal input is six milliwatts. In practice the headset assembly is amply gasketed and hermetically sealed against ambient elements and pressures.

Significant portions of headset 10 are illustrated in exploded perspective array in FIG. 5, with details as watersealing gaskets and screws omitted for reasons of clarity of presentation. The lower part is the common frame or housing 23 that contains at its bottom the integral tissuecontacting diaphragm 27. The apertured boss on diaphragm 27 mounts the inertial microphone element 24, as aforesaid; its armature being seen separately therefrom. Element 24 is broken-away to show the interior coil 41, magnet 42 and pole piece 43 held by mounting block 44. Reproducer 25 is similar thereto, with armature 45 on top that attaches with disc 31 across a coupling spacer 46. A protective frame 47 is used on unit 25.

An exterior bezel 43 or clamp ring is pressed against the rim of circular diaphragm 29. Six machine screws hold the assembly (10) together (with suitable gaskets therewith), through apertures shown in bezel 48 and diaphragm 29 into threaded holes 49, 49 of frame 23, The diaphragms 27 and 29, 31 for the variable reluctance inertial units 24 and 25 each has several times the area as it respective unit. This aids the overall transducer efficiency herein as microphone and as reproducer, and are in a composite, compact array. The mechanical resonant frequency of the exemplary reproducer (25) per se is placed in the range of 600 to 900 cycles per second; and that of the microphone (24), in the range of 1800 to 2200 cycles per second. The reproducer system operated in water has subjectively provided acoustical output over 600 to 10,000 cycles per second within 10 db. The result is thus clear, with good articulation. There is no interference or operational deterioration between the assembled transducers 24 and 25 hereof. The composite headset 10 is useful, practical, and practically weightless when submerged.

FIG. 6 illustrates in cross-section a modified voice communication device 50 containing a single transducer 51 for underwater use. It is otherwise similar to headset 10. The single variable reluctance inertial reaction transducer 51 is secured to the thin flexible diaphragm 52-disc 53 combination by machine screws 54, as in headset 10. Transducer 51 may be mounted off center as shown, or centrally of disc 53. The diaphragm 52 is attached to the hollow housing 60 across an annular gasket 55 by clamp ring 56 through machine screws 57, 57. The coil leads 62 of reproducer 51 connect to an exterior electrical circuit that operates the device 50. A terminal board 63 electrically connects coil leads 62 to the wires 64 of exterior cable 65.

Device 50 may be used in the manner described for headset 10. It is strapped upon the head of the diver or swimmer by straps attached to strap mounts 59, 59 on housing 60. The base 61 is substantial in thickness, and positions the device upon the head when used as a soundreproducer only. Such mounting exposes the driver-piston 53 outwardly in coupling with the water when submerged. The efiiciency and mechanical resonant frequency of the reproducer 50 unit is similar to that described hereinabove for reproducer 25. The sound generated thereby in the water is significant, clear and with good intelligibility and articulation. The sound produced in this manner, as with a six milliwatt input, radiates at least three feet effectively, as hereinabove set forth.

The transducer device 50 may instead be used as an inertial variable reluctance microphone. For such operation, device 50 is strapped with the disc 53 touching the head, instead of base 61. The skull vibrations during speech are imparted to disc 53 and in turn to inertial reaction transducer 51. Transducer 51 translates its vibrations into voice signals that are conducted to a locally carried amplifier for transmission beyond in a well known manner. In this operational mode of device 50, transducer 51 can be used both as a microphone and as a reproducer. The circuit is arranged on a push-to-talk basis to connect it for microphone operation, as aforesaid. When the push button is released, the transducer 51 receives signals to be converted into sound vibrations thereby. Such vibrations are imparted to the skull through the contacting disc 53, as will now be understood by those skilled in the art.

In essence, the invention communication devices and comprise variable-reluctance inertial-type transducers 24, 25 and 51. These are operatively suspended or otherwise dynamically coupled to the housing base (27), or to an essentially pliant diaphragm as 29 or 52. The transducers are arrayed interiorly of the housings 23, and in the exemplary embodiments are gasketed for hermetic sealing. Enlarged FIGS. 7 and 8 illustrate the relation of inertial transducer 51 to device 50, and its elastic mechanical coupling to diaphragm-disc 5253.

The theory, operation and construction of the inertial transducers per se, are well known in the art. The body 67 of the transducer 51 contains a coil winding (66) therein, connecting with the leads 62, 62 and a pole piece structure (not shown), When acoustic signal currents are fed itno coil 66, corresponding variable electromagnetic attraction occurs between body-mass 67 and the armature '70, as understood by those skilled in the art. Armature 70 contains two arm cut-outs 71, 72 that provide a centilevered elastic relation with its central section 75. Arms 71, 72 are respectively fastened to body-mass 67 by machine screws 73, 74 through apertures 76, 77.

The armature 70 is firmly secured to disc-diaphragm 52-53 by machine screws 54, 54, with spacer 78 therebetween. The centrol armature section 75 contains suitable threaded apertures therefor. In operation, signals introduced to coil 66 of transducer 51 create a correspondingly variable flux field and corresponding variable attractive force between body-mass 67 and suspended armature 70. There results a sympathetic mechanical inertial reaction or vibration between body-mass 67 on the one side; and central armature section 75, spacer '78, diaphragm 52 and attached disc 53 on the other side. The arms 71, 72 elastically couple these two mass assemblies for their mutual dynamic reaction.

In use, the ambient water pressure on disc-diaphragm 52 53, is taken into account to proportion the mass factors of the unit for eflicient sound production and transmission through the water. Similarly, for the other applications set forth hereinabove. The electromagnetic inertial variable reluctance transducer 51 is thus suspended within case 60 for its mutual vibrational action (across the elastic coupling provided by arms 71, 72) with external diaphragm 52 and disc 53. The construction and arrangement of dual unit It] with the two transducers 24- and 25 (see FIGS. 4 and 5) corresponds to that of a single transducer unit 50.

Although the present invention has been described in conjunction with exemplary embodiments thereof, it is to be understood that modifications and variations thereof, such as in construction and application, may be made that fall within the spirit and scope of the invention, as set forth in the appended claims.

What is claimed is:

1. An underwater communications headset of the character described comprising a first and a second diaphragm, a housing supporting said diaphragms in spaced parallel array, a first and a second inertial reaction variable reluctance transducer contained within said housing and respectively coupled to said first and second diaphragms within said housing, said first transducer being adapted to function as a microphone and said second one as a sound reproducer.

2. An underwater communications headset as claimed in claim 1, in which said first diaphragm secured with the microphone transducer is of sufficiently rigid construction for firm operative contact with the users head.

3. An underwater communications headset as claimed in claim 1, in which said second diaphragm secured with the reproducer transducer is of suificiently pliant construction for generating sound vibrations when submerged in water, and a substantially flat member joined with the central region of said second diaphragm on the outer side thereof for operative contact with the water when submerged to provide piston displacement action for eificient sound generation therein.

4. An underwater communications headset as claimed in claim 1, in which said first and second transducers are respectively coupled to said first and second diaphragms on their facing sides within said housing.

5. An underwater communications headset as claimed in claim 4, in which said first and second transducers are arranged in offset side-by-side relation.

6. An underwater communications headset as claimed in claim 1, in which said first diaphragm secured with the microphone transducer is of relatively rigid construction and integral with said housing for operative contact with the users head; and said second diaphragm secured with the reproducer transducer is or" relatively pliant construction, and a substantially fiat member joined with the central region of said second diaphragm on the outer side thereof for operative contact with the water when submerged to provide efficient sound generation therein.

7. An underwater communications headset as claimed in claim 3, in which said flat member is relatively stiff and is a mass-load for the attached second diaphragm.

8. An underwater communications headset as claimed in claim 6, in which said flat member is relatively stiff and is a mass-load for the attached second diaphragm, whereby the operation of said first and second transducers are electromechanically related through the mechanical filtering action of the composite second diaphragm-member.

9. An underwater communications headset as claimed in claim 3, in which said fiat member is in the form of a plane disc that serves as a piston sound generator when submerged in the water.

10. An underwater communications headset as claimed in claim 6, in which said flat member is in the form of a plane disc that serves as a piston sound generator when submerged in the water.

11. An underwater communications headset as claimed in claim 7, in which said flat member is in the form of a plane disc that serves as a piston sound generator when submerged in the water.

12. An underwater communications headset as claimed in claim 8, in which said fiat member is in the form of a plane disc that serves as a piston sound generator when submerged in the water.

13. An underwater communications headset comprising a diaphragm, a housing with an open end supporting said diaphragm thereat, said diaphragm being of compliant construction, a substantilly flat member joined with the central region of said diaphragm on its outer side, an inertial reaction variable reluctance electro-acoustic transducer contained within said housing, said transducer having an electromagnetic body and an armature elastically coupled closely therewith, said armature being fastened to said diaphragm at its interior side, whereby inertial reaction vibrations are translated between the diaphragm-member combination and said body across said armature corresponding to vibrations initiated in either.

14. An underwater communications headset as claimed in claim 13, in which said housing is formed with a base substantially parallel to said diaphragm, and said electromagnetic body contains a coil responsive to electrical acoustic signals, whereby when said base is in contact with ones head inertial reaction vibrations are induced nation during its reproducer mode to provide efiicient acoustic reproduction of the signals when submerged in water.

15. An underwater communications headset as claimed in claim 13, in which said flat member is relatively stiff and is a mass-load for the attached pliant diaphragm.

16. An underwater communications headset as claimed in claim 14, in which said fiat member is in the form of c r y transd o y to a d phr mrmem o ia to or a plane disc that serves as a piston sound generator when submerged in the water.

17. An underwater communications headset as claimed in claim 13, in which said electromagnetic body contains a coil, whereby said member is vibrated in accordance with ones speech when in contact with ones head in the microphone mode, correspondingly vibrating said body through inertial reaction forces and thereby generating electrical signals in said coil in correspondence with the speech.

References Cited UNITED STATES PATENTS 2,958,078 10/1960 Hickman. et al 340-8 RODNEY D. BENNETT, Primary Examiner.

I, G. BAXTER, Assistant Examiner.

US. Cl. X.R.

7 ,7 9 7 21 8 87 C aw rd-i i 340+5 to 

